I have been trying to start up my mac in recovery mode to wipe it and reinstall everything and I keep getting a grey screen with a circle and a line through the circle

I have been trying to start up my mac in recovery mode to wipe it and reinstall everything and I keep getting a grey screen with a circle and a line through the circle.

I have been able to successfully restore from the external hard drive I bought a few months ago to try and resolve the ongoing issues of the slowness and basically inability to use anything on my mac successfully without it crashing. I am trying to start it up using the command and R but it still goes to the grey screen with the circle. I really think I should be able to get a few more years out of this because I only bought it about 5 or 6 years ago and it did completely crash right before the warranty ran out and they replaced the hard drive at that time, so the hard drive is not that old. Any suggestions? No warranty on my mac and I desperately need it working as I can't afford to replace it right now. It was backed up before this happened so I am not worried about backing it up before I wipe the hard drive and reinstall the OS.